This invention relates to catheters and particularly to urethral drainage catheters of the balloon type. Such catheters are used extensively for bladder drainage, for example, in cases of patient incontinence or when, for any reason, he cannot release urine from his bladder because of a constriction in his urethra. The catheter is introduced into the bladder via the urethra which, in the male, is a relatively tortuous tube of varying cross-sectional dimensions which is normally collapsed along most of its length. The upper portion of the urethra has sphincters or valves where it enters the bladder neck. In the female, the urethra is shorter and straighter but otherwise functionally the same.
At best, the use of such a catheter is quite uncomfortable to the patient. In order to minimize the discomfort and to facilitate insertion and proper placement of the catheter, it should be of smooth and rounded contour and should be as slender as possible. The drainage eyes in the tip should be shaped to provide flow passage for the urine and should have no sharp edges. There should be no shoulders on the catheter facing either in the forward or in the backward direction which might hinder insertion or removal of the catheter. While the catheter should bend easily to follow the tortuous path of the urethra, it also should have good cross-sectional stability to prevent kinking and collapse in the areas of the urethra which may be constricted.
When properly positioned, the tip of the catheter protrudes into the patient's bladder. Under normal circumstances, the bladder is emptied voluntarily from time to time by controlling the sphincter muscles. However, when the catheter is in place, the bladder is drained continually and thus is as empty as the location of the drainage holes or eyes of the catheter tip permits. When empty, the bladder walls rest on the catheter tip and a smooth tip will minimize the likelihood of irritation and trauma to the bladder wall. It also is desirable that the drainage eyes in the tip be located as low in the bladder as possible to minimize the amount of undrainable urine in the bladder.
In order to securely anchor the catheter in place, the catheter includes an expandable balloon located behind the drainage eyes. The balloon PG,3 is inflated only after the catheter is in proper position. The balloon is inflated (to anchor) or deflated (for removal) by means of elongate inflation lumens formed through the body of the catheter and which communicate with the balloon.
The manufacture of urethral catheters having the foregoing desirable characteristics has not been without difficulty. In general, such catheters have been formed from latex and in a complicated, time-consuming, dipping process well known to those skilled in the art. Because of the relatively flexible and elastic nature of the latex, such catheters tend to bend or kink. As a result it has not been possible to form the various openings and passageways in the catheter to be as large as would be desirable because that would further reduce the stiffness of the catheter. These limitations also restrict the number of inflation lumens which can be employed. Typically, there are no more than two inflation lumens and sometimes there is only one. This can result in serious difficulties when it is desired to remove the catheter should the inflation lumens become blocked and fail to permit deflation of the balloon. Still another difficulty with prior urethral catheters is that the latex material can react with the urine and is quite wettable which makes for patient discomfort when the catheter is advanced within the urethra. Also among the difficulties with latex catheters is that the balloons sometimes malfunction, by rupturing or failing to deflate.
These and other commonly encountered difficulties of latex urethral catheters can be minimized significantly by making the catheter from a more biologically inert material, such as silicone rubber and I have made and described such an invention in my U.S. Pat. No. Re. 27,910. As described more fully in that patent, a catheter tip and balloon flap are molded as an integral, one-piece unit which is attached to the leading end of the catheter tube, also made from silicone rubber. The resulting catheter is shoulderless, is of good cross-sectional stability and enables the various openings and lumens to be of an enlarged size. Additionally, the catheter described in my foregoing patent is more easily and economically manufactured than the typical prior dipped latex-type catheters.
While the catheter described in my foregoing U.S. patent is a significant advance over the prior latex catheters, it nevertheless has required some compromise because the tip preferably is relatively inelastic and stiff while the balloon portion desirably is elastic and resilient. Where the tip and balloon are molded from the same material in a one-piece, unitary construction, the elasticity and stiffness of the tip and balloon material are the same. It is among the primary objects of the present invention to provide a urethral catheter having a one-piece, molded tip and integral balloon in which each has the ideal properties of stiffness and/or elasticity.